According to the RP-060846 (Proposed WID for 64QAM for HSDPA (high rate downlink packet access)) of the 3rd Generation Partnership Project (3GPP), HSPA+ will add a new high order modulation such as 64 Quadrature Amplitude Modulation (64QAM). However, the present 3GPP has not defined how to add 64QAM into the new specification.
According to the section 4.5.4.4 in the 3GPP TS 25.212 V7.7.0, the physical layer HARQ module of the base station (Node B) should perform bit collection for the data after the second rate matching in the HARQ. However, the present bit collection module only supports Quadrature Phase Shift Keying modulation (QPSK) and 16QAM. FIG. 1 and FIG. 2 respectively show some methods for bit collection of QPSK and 16QAM in the prior art.
The physical layer based on 3GPP Release 7 (and later ones) will use high order modulation such as 64QAM (or even 256QAM, 1024QAM or 4096QAM), yet the present 3GPP has not determined how to use 64QAM, that is, its physical layer specification has not be formed yet. In order to make the HSPA+ system completely support 64QAM and still be compatible with the present HSDPA, a method and apparatus for bit collection in HARQ is disclosed.